1. Field of the Invention
The present disclosure relates to a silicon carbide semiconductor device.
2. Description of the Background Art
An exemplary semiconductor device employing silicon carbide is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). A MOSFET is a semiconductor device for controlling electric current between a source electrode and a drain electrode by controlling whether to form an inversion layer in a channel region in accordance with a threshold value of gate voltage. In this MOSFET, in the on state in which an inversion layer is formed in the channel region, electrons introduced into a silicon carbide layer from a source electrode sequentially pass through a source region, a body region (channel region), and a drift region in the silicon carbide layer, and then reach a drain electrode.
For example, Hiroyuki Matsunami, Noboru Otani, Tsunenobu Kimoto, and Takashi Nakamura, “Technology of Semiconductor SiC and Its Application”, Second Edition, Nikkan Kogyo Shimbun, September 2011, pp. 304-305 discloses a technique of forming an electrode in contact with each of an n type source region and a p type contact region in a MOSFET (SiC-MOSFET) employing silicon carbide. In this technique, contact resistance with respect to the p type contact region becomes higher than contact resistance with respect to the n type source region, but the electrode can be in ohmic contact with each region. Meanwhile, contact resistance of a titanium aluminum silicon electrode with respect to each of an n type region and a p type region is disclosed in Hideto Tamaso, Shunsuke Yamada, Hiroyuki Kitabayashi and Taku Horii, “Ti/Al/Si Ohmic Contacts for Both n-Type and p-Type 4H—SiC”, Materials Science Forum, Switzerland, Trans Tech Publications Inc., February, 2014, Vols. 778-780, pp. 669-672.